This invention relates to the use of beta-agonists, namely a beta-2 agonist to enhance the effects of a strength training program or maintain endurance during periods of inactivity.
When combined with exercise training, the program results in increased power and endurance.
In the past, it has been contended that the intravenous use of dobutamine (a primary beta-1 agonist) has resulted in the maintenance of aerobic capacity in subjects placed at bedrest (see the Sullivan et al. publication entitled "Prevention of Bedrest-induced Physical Deconditioning by Daily Dobutamine Infusions".)
Inactivity or microgravity will result in muscle weakness and atrophy. During bedrest, muscle will loose 10-15% of strength per week and 50% in three to five weeks. Muscle bulk may be reduced by 50% in two months. Antigravity muscles such as quadriceps or gastrocnemius are affected the most.
Similar loss of strength is incurred during space flight. For example, measurements made before and after Skylab missions found a 25% decrease in gastrocnemius strength and decreased calf volume indicating muscle mass loss.
Decreases in maximal oxygen uptake and increased cardiovascular response to submaximal workloads occur quickly during bedrest. In some common bedrest studies of varying patients, there was found to be approximately a 9% decrease per week in aerobic capacity. Thus, the decrease in aerobic capacity with bedrest is significant. Investigations of the mechanisms have demonstrated that reduced plasma volume and cardiac stroke volume is the major mechanism. The reduction in aerobic capacity with inactivity can be effected by fitness level. Microgravity, especially when prolonged, has resulted in a similar reduction of aerobic capacity as bedrest.
Exercise has been utilized to prevent and reverse bedrest-induced changes in muscle strength and aerobic capacity. Isometric and isotonic exercise increase both strength and power.
Exercise programs have been utilized in U.S. and Russian space flights. Presently, space shuttle orbiter crew exercised for approximately one hour every other day and payload crew exercised every third day. In extended duration missions, the crews exercised two hours per day, increasing to about four hours per day, several weeks before returning to Earth. Resistance training in space such as on Skylab, has mitigated the loss of strength. Overall, exercise countermeasures have only been partially successful in preventing loss of strength, or loss of aerobic capacity.
An aerobic conditioning effect on Earth will depend on the intensity, frequency, and duration of exercise. It appears that as little as one to two workouts per week for 10-15 minutes at low workloads can achieve some conditioning effect but this will depend on the fitness level of the subject. For trained individuals, a threshold of intensity may be necessary. Intensity levels close to the anaerobic threshold appear most effective.
Beta-2 agonists exist in many forms and are used routinely for relief of bronchospasm in the treatment of airways disease such as asthma or chronic obstructive pulmonary disease. For example, isoproterenol is available in a sublingual form, a metered dose inhaler, and as solution. There are several beta-2 agonists such as albuterol that are available in tablet, solution, and metered dose inhaler form. The tablet forms of medication are safe, easy to use and do not require the level of monitoring that intravenous dobutamine or high dose nebulized solutions require.
It is an object of the present invention to devise a program for maintaining the strength and endurance for patient's subjected to bedrest for extended periods of time.
It is another object of the present invention to increase the strength, endurance and aerobic capacity of an individual alone or in combination with appropriate exercise.